Field Test · Studio Gear Review
Superlux HD-668 B
Technical evaluation of the Superlux HD-668 B semi-open over-ear headphones
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Spec Sheet
- Circumaural
- Semi-open
- Dynamic
- Self-adjusting headband for comfort
- Peak SPL: 98 dB
- Impedance 56 Ohm
- Frequency range: 10 – 30,000 Hz
- Power capacity: 300 mW
- Detachable cable
- 1 m and 3 m cables with 3.5 mm stereo jack
- Weight with cable: 251 g
- Weight without cable: 228 g
- Includes: 6.3 mm stereo jack and bag adaptor
Studio Log
| Available since | March 2010 |
|---|---|
| Item number | 240342 |
| Sales Unit | 1 piece(s) |
| Design | Over-Ear |
| System | Semi Open |
| Impedance | 56 Ohms |
| Frequency range | 10 Hz – 30000 Hz |
| Adaptor | Yes |
| Replaceable Cable | Yes |
| Colour | Black |
| Max. SPL | 98 dB |
| Type Of Connector | Mini Jack |
| Weight | 228 g |
Demo Footage
Field Photography
QC Pass — Field Test
Customer Review Summary
Introduction
Released in March 2010, the Superlux HD-668 B is a budget-friendly semi-open circumaural headphone priced at approximately £26. It offers a dynamic system with 56 Ohms impedance, a frequency range of 10 Hz to 30,000 Hz, and detachable cables. Its design promises decent comfort and a sound profile suitable for various casual and some studio applications.
Build and Comfort
The headphones feature a largely plastic construction, making them lightweight at 228 grams (without cable). The semi-open, circumaural design surrounds the ears completely with large earcups. Although the build is adequate for the price category, the use of relatively brittle plastic components is evident and can lead to durability concerns over time.
The headband is self-adjusting but exerts noticeable clamping force. This can cause discomfort, especially over extended listening periods. Users often report significant pressure on the ears which some alleviate by gently widening the headband. The supplied artificial leather earpads tend to promote sweating and are somewhat harsh on the skin, prompting many to replace them with velour pads designed for the AKG K-240 model, which are compatible and considerably improve comfort.
The headset includes two detachable cables of 1 and 3 metres, both with 3.5 mm stereo jacks, plus a 6.3 mm adapter and a carrying pouch. The detachable cables are a practical feature, reducing the risk of total failure and facilitating easier replacement compared to many low-cost competitors.
Sound Performance
The HD-668 B produces a clear and defined sound, distinctly better than many budget headphones. Its frequency response is relatively balanced, with good clarity in the mid and high frequencies and an extended range reaching 30 kHz. However, the bass tends to be somewhat elevated and loose, lacking precision in the very lowest registers. This bass emphasis can mask subtle low-end details.
Compared to older high-end models like the Sennheiser HD 430, the Superlux delivers higher sensitivity and usability with portable devices such as smartphones. The mids and highs are generally well resolved, though some users note a slightly sharp peak around 5 to 8 kHz that can cause listening fatigue unless equalised.
The soundstage is reasonable for a semi-open design but not as expansive or airy as pricier or fully open headphones. Imaging and separation are acceptable, with percussive sounds not as punchy as on higher-tier models. For gaming, the spatial clues are sufficient for directional awareness, supporting competitive gameplay.
Use with Equalisation
Many listeners find the sound quality benefits greatly from software correction like Sonarworks calibration, which smooths the frequency response and creates a more natural tonal balance. Without such calibration, the ears note some inconsistency in the treble region and an imbalanced bass presentation. The investment in such software may edge the performance closer to headphones costing considerably more.
Practical Considerations
- Durability: While the plastic parts are fragile, the design tolerates rough handling fairly well under normal use. The removable cable system is particularly resilient.
- Comfort modifications: The stock headband and pads are compromises. Upgrading to velour pads and gentle headband adjustment significantly improves wearability.
- Isolation: The semi-open design leaks sound, making these unsuitable for recording environments where microphone bleed is a concern.
- Amplification: The 56 Ohm impedance allows easier use with smartphones and portable devices without an external amplifier. However, a higher quality amp improves dynamic range and detail.
- Accessories: Inclusion of two cables, an adaptor, and a carrying pouch is generous for the price.
Comparison and Overall Assessment
The Superlux HD-668 B falls short of high-end professional headphones but outperforms many similarly priced alternatives. It delivers a clear, spacious sound with a slightly fun tonal signature prioritising upper midrange and bass. However, comfort and build quality restrict its appeal for long, demanding sessions without modification. For users seeking a highly affordable introduction to semi-open headphones, it offers remarkable value.
Those looking for accurate tracking or mixing should consider alternative or more expensive options, or use equalisation software to correct the frequency response. Gaming and casual listening are where the HD-668 B excels, providing an engaging soundstage and decent spatial precision for its price.
Conclusion
The Superlux HD-668 B remains an exceptional low-budget headphone with sound quality often exceeding expectations. Despite some ergonomic and material compromises, it offers a great entry-level option for home listening and gaming with robust connectivity features. A simple pad upgrade and careful handling can extend its usefulness substantially, making it a smart choice for cost-conscious buyers prioritising audio performance over premium finishes.
